Written by William G. Handlos, P.E.
Lightweight Construction Mats
Construction access in soft soils present a common challenge engineers and project managers face while attempting to complete a project on-time and within budget while avoiding scheduling delays and associated costs. These soft soil sites may also be located in remote, difficult to access areas making construction impossible without a good site access system. Popular construction mat systems are made out of a range of materials including timber, laminate, steel and composite mats. They can be effective, but are also costly. They can also put laborers at risk as they require heavy equipment to install. The ideal mat system for access road construction would be designed to have a high utility-to-weight ratio and would deliver an eco-friendly alternative to current technology.
A lightweight construction mat system made from high density polyethylene (HDPE), GEOTERRA®, was created by Presto Products in 2003 to meet the needs of major oil and gas companies working in remote areas of the Amazon jungle. Transporting materials to these sites by helicopter precipitated the need for light, yet strong mats for work platforms and roadways. As the first of its kind, the mats capitalize on the sustainable characteristics of recycled polyethylene and offer an efficient, lightweight design for a variety of remote access applications.
Typical construction mat applications include working platforms for oil and gas exploration as well as maintenance and access roads to transmission lines, pipelines, wind power generation, and mining operations. In addition, construction mats have also been used in a variety of other applications including walkways in soft soils, storage pads and helipads. The GEOTERRA® mat system may also be used as a tracking pad to remove excess soil from vehicle treads. This may mitigate problems associated with the use of traditional aggregate tracking pads which are difficult to work with, costly and hard to remove.
Lightweight HDPE mats are installed without heavy equipment. This decreases the risk of injury and minimizes equipment needs for construction site access. Utilizing a steel torsion tightened “PadLoc®” these mats provide strong connections for load transfer between sections and may be pre-assembled for quick installation in remote site applications.
This lightweight mat system does not degrade, weather, or leach into the subsurface as it is made from up to 97% recycled polyethylene. The ability to dissipate pore water pressure over the existing soil is essential to providing a safe, dry working surface for construction equipment and workers. The high strength geotextile underlayment eliminates soil upwelling in open cells and will allow the system to “float” over poor soils If the underlying soil is pervious, the open cell mat design allows it to act as a porous pavement which reduces the necessity for extra drainage components. If that is not the case, a one or two-sided geocomposite may be used in conjunction with the mat system to effectively direct the precipitation off of the working surface.
Even the most difficult site challenges can be overcome by combining lightweight portable mat systems with the correct under layer and anchoring system. Very soft soils with a CBR (California Bearing Ratio) of two or less may require additional load support which may be provided by cellular confinement (geocell) systems.